Stylus and sensor control circuit

ABSTRACT

A stylus includes a first transmission circuit, a second transmission circuit, and a control circuit which controls the first and second transmission circuits according to a first transmission mode in which the control circuit controls the first transmission circuit to transmit a first downlink signal from a tip electrode and controls the second transmission circuit to not transmit a second downlink signal from a tail electrode, a second transmission mode in which the control circuit controls the first transmission circuit to not transmit the first downlink signal from the tip electrode and controls the second transmission circuit to transmit the second downlink signal from the tail electrode, and a third transmission mode in which the control circuit controls the first transmission circuit to transmit the first downlink signal from the tip electrode and controls the second transmission circuit to transmit the second downlink signal from the tail electrode.

BACKGROUND Technical Field

The present disclosure relates to a stylus and a sensor control circuit.

Background Art

There is a known stylus for an electronic device modeled on a pencilwith an eraser.

A stylus which includes an antenna also on a tail side opposite a tipside from which a pen signal is transmitted and which can transmit aneraser signal from the antenna is disclosed in each of U.S. Pat. No.5,793,360 and U.S. Patent Application Publication No. 2018/0052534.

To reduce a time lag between a point in time of contact to the stylusand a point in time of position detection by an electronic device, thepen signal or the eraser signal (hereinafter, collectively referred toas a “downlink signal”) may be transmitted even when the stylus is in aso-called hover state. This improves operation response of the stylus,but consumption of electrical energy increases with an increase intransmission time of the downlink signal.

The problem does not occur in a system triggered by energy provided fromthe outside to generate and transmit the downlink signal, such aselectromagnetic radiation (EMR: registered trademark) described in U.S.Pat. No. 5,793,360. However, the problem may occur in an active systemthat uses electrical energy stored in the stylus to generate andtransmit the downlink signal. Particularly, the active-type stylusdescribed in U.S. Patent Application Publication No. 2018/0052534simultaneously transmits two types of downlink signals so as to handlecontact on either one of the tip side and the tail side, and thisfurther increases the consumption of electrical energy.

BRIEF SUMMARY

An object of the present disclosure is to provide an active-type stylusand a sensor control circuit capable of reducing the consumption ofelectrical energy while securing the operation response in aconfiguration in which downlink signals can be transmitted from both thetip side and the tail side.

A stylus according to a first aspect of the present disclosure includesa cylindrical housing, a tip portion provided on a tip side of thehousing and including a tip electrode, a tail portion provided on a tailside of the housing and including a tail electrode, a power circuitprovided in the housing, a first transmission circuit which, inoperation, receives power from the power circuit and generates a firstdownlink signal that is transmitted toward an outside of the housingthrough the tip electrode, a second transmission circuit which, inoperation, receives power from the power circuit and generates a seconddownlink signal that is transmitted toward the outside of the housingthrough the tail electrode, wherein the second downlink signal isdifferent from the first downlink signal, and a control circuit which,in operation, controls the first transmission circuit and the secondtransmission circuit according to a plurality of transmission modes. Thetransmission modes include a first transmission mode in which thecontrol circuit controls the first transmission circuit to transmit thefirst downlink signal from the tip electrode and controls the secondtransmission circuit to stop transmission of the second downlink signalfrom the tail electrode, and a second transmission mode in which thecontrol circuit controls the first transmission circuit to stoptransmission of the first downlink signal from the tip electrode andcontrols the second transmission circuit to transmit the second downlinksignal from the tail electrode. In a hover state in which both the tipportion and the tail portion do not contact a touch surface of anelectronic device including a touch sensor, the control circuit controlsaccording to the first transmission mode or the second transmission modebased on a determination regarding a grasp state of the housing.

A sensor control circuit according to a second aspect of the presentdisclosure is a circuit connected to a sensor electrode, the sensorcontrol circuit comprising:

-   -   a processor; and a memory device storing instructions that, when        executed by the processor, cause the sensor control circuit to:        receive a first downlink signal and a second downlink signal        from a stylus through the sensor electrode, the first downlink        signal being different from the second downlink signal, generate        an uplink signal including data corresponding to the first        downlink signal or the second downlink signal, and transmit the        uplink signal through the sensor electrode, wherein the stylus        is configured to transmit the first downlink signal through a        tip electrode provided on a tip side of a housing of the stylus,        and to transmit the second downlink signal through a tail        electrode provided on a tail side of the housing of the stylus.

According to the present disclosure, consumption of electrical energycan be reduced while operation response is secured in the configurationin which the downlink signals can be transmitted from both the tip sideand the tail side.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall configuration diagram of a position detectionsystem provided with a stylus according to a first embodiment;

FIG. 2 is a schematic block diagram of an electronic device illustratedin FIG. 1;

FIG. 3A is a side view of the stylus illustrated in FIG. 1;

FIG. 3B is a partial development diagram of a housing of the stylusillustrated in FIG. 1;

FIG. 4 is an electrical block diagram of the stylus illustrated in FIG.1;

FIG. 5 is a flow chart for describing an operation of the stylusaccording to the first embodiment;

FIG. 6A depicts an example of a determination method of a grasp state;

FIG. 6B depicts an example of a determination method of a grasp state;

FIG. 6C depicts an example of a determination method of a grasp state;

FIG. 7A is a side view of the stylus according to a first modificationof the first embodiment;

FIG. 7B is a partial development diagram of the housing of the stylusaccording to the first modification of the first embodiment;

FIG. 8A is an external view of a stylus according to a secondmodification of the first embodiment;

FIG. 8B is an external view of the stylus according to the secondmodification of the first embodiment;

FIG. 9 is an external view of a stylus according to a second embodiment;

FIG. 10 is an electrical block diagram of the stylus illustrated in FIG.9; and

FIG. 11 is a flow chart for describing an operation of the stylusaccording to the second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A stylus and a sensor control circuit according to the presentdisclosure will be described with reference to the attached drawings.Note that the present disclosure is not limited to the followingembodiments and modifications, and it is obvious that the presentdisclosure can be freely changed without departing from the scope of thedisclosure. The configurations may also be arbitrarily combined as longas the combination is not technically contradictory.

First Embodiment

First, a stylus 16 according to a first embodiment will be describedwith reference to FIGS. 1 to 6C.

<Overall Configuration of Position Detection System 10>

FIG. 1 is an overall configuration diagram of a position detectionsystem 10 provided with the stylus 16 according to the first embodiment.The position detection system 10 basically includes an electronic device14 including a display panel 12, and the stylus 16 that is a pen-shapedpointing device.

The electronic device 14 includes, for example, a tablet terminal, asmartphone, or a personal computer. A user Us grasps the stylus 16 withone hand and moves the stylus 16 while pressing a pen nib against atouch surface 18 of the display panel 12, so that the user Us can writea drawing or a character on the electronic device 14.

The stylus 16 can communicate with the electronic device 14 in onedirection or both directions. Hereinafter, a signal transmitted by thestylus 16 toward the electronic device 14 will be referred to as a“downlink signal,” and a signal transmitted by the electronic device 14toward the stylus 16 will be referred to as an “uplink signal” in somecases. Note that the stylus 16 is an “active type” stylus which useselectrical energy stored in the stylus 16 to actively generate a signaland which transmits the signal as a downlink signal toward theelectronic device 14.

<Configuration of Electronic Device 14>

FIG. 2 is a schematic block diagram of the electronic device 14illustrated in FIG. 1. The electronic device 14 includes sensorelectrodes 200, a sensor control circuit 202, and a host processor 204.Note that an x-direction and a y-direction illustrated in FIG. 2respectively correspond to an X-axis and a Y-axis of a Cartesiancoordinate system defined on a plane formed by the sensor electrodes200.

The sensor electrodes 200 are a plurality of electrodes arranged betweenthe display panel 12 and the touch surface 18 (FIG. 1). The sensorelectrodes 200 include a plurality of X electrodes 200 x for detectingthe X-coordinate (position in the x-direction) and a plurality of Yelectrodes 200 y for detecting the Y-coordinate (position in they-direction). The X electrodes 200 x are provided to extend in they-direction and are arranged at regular intervals in the x-direction.The Y electrodes 200 y are provided to extend in the x-direction and arearranged at regular intervals in the y-direction.

The sensor control circuit 202 is an integrated circuit that can executefirmware 206 and is connected to each of the plurality of electrodesincluded in the sensor electrodes 200. The firmware 206 includesprocessor-readable instructions stored in a memory device 208 that, whenexecuted by a processor 210, causes the sensor control circuit 202 torealize a touch detection function of detecting a touch by the user Usand a pen detection function of detecting a state of the stylus 16.

The touch detection function includes, for example, a two-dimensionalscan function of the sensor electrodes 200, a creation function of aheat map (two-dimensional position distribution of detection level) onthe sensor electrodes 200, and a region classification function (forexample, classification of fingers and palm) on the heat map. The pendetection function includes, for example, a two-dimensional scanfunction of the sensor electrodes 200, a reception and analysis functionof the downlink signal, an estimation function of the state (forexample, position, posture, and pen pressure) of the stylus 16, and ageneration and transmission function of the uplink signal including aninstruction for the stylus 16.

The host processor 204 is a processor including a CPU (CentralProcessing Unit) or a GPU (Graphics Processing Unit). The host processor204 reads a program from a memory not illustrated and executes theprogram to generate, for example, digital ink by using data from thesensor control circuit 202.

<Configuration of Stylus 16>

FIGS. 3A and 3B are external views of the stylus 16 illustrated inFIG. 1. More specifically, FIG. 3A is a side view of the stylus 16, andFIG. 3B is a partial development diagram of a housing 20.

As illustrated in FIG. 3A, the stylus 16 includes the housing 20 in acylindrical shape, a tip portion 22 provided on one end side(hereinafter, referred to as a tip side) of the housing 20, and a tailportion 24 provided on the other end side (hereinafter, referred as atail side) of the housing 20.

The cross-sectional shape of the housing 20 is, for example, a Reuleauxtriangle. The shape allows a user to easily hold the stylus 16 andreduce fatigue of the hand.

The tip portion 22 in a roughly conical shape includes a tip electrode22 e made of a conductive material and a tip cover 22 c covering part orall of the tip electrode 22 e. The tip electrode 22 e is an electrodethat outputs a pen signal described later and is attached to a core notillustrated. A tip side sensor group 26 is provided on the tip side ofthe housing 20. The tip side sensor group 26 includes an end portionsensor 27 that detects pressing toward the tip portion 22 and a contactsensor 28 that detects contact by a human body.

The tail portion 24 in a roughly conical shape includes a tail electrode24 e made of a conductive material and a tail cover 24 c covering partor all of the tail electrode 24 e. The tail electrode 24 e is anelectrode that outputs an eraser signal described later and is attachedto a core not illustrated. A tail side sensor group 30 is provided onthe tail side of the housing 20. The tail side sensor group 30 includesan end portion sensor 31 that detects pressing toward the tail portion24 and a contact sensor 32 that detects contact by a human body.

The end portion sensor 27 (31) is, for example, a pressure sensor usinga variable capacitor that detects a change in capacitance generated bypressing toward the tip portion 22 (tail portion 24). Note that the endportion sensors 27 and 31 may be pressure sensors using another systemor may be pressure switches that are switched on and off on the basis ofpredetermined pressing (threshold).

The contact sensors 28 and 32 are, for example, self-capacitance ormutual-capacitance touch sensors. Note that the contact sensors 28 and32 may be sensors (specifically, pressure sensors or heat sensors) thatdetect energy supplied by contact by a human body or may be opticalsensors that detect a contact position of a human body. The contactsensors 28 and 32 may be housed in the housing 20 or may be attached toan outer peripheral surface of the housing 20 according to the type ofdetection system.

As illustrated in FIG. 3B, the contact sensor 28 on the tip sideincludes rectangular detection regions R1 to R3 extending in an axialdirection of the housing 20 and curved in a circumferential direction.The detection regions R1 to R3 in three locations are arranged in themiddle of apexes adjacent to each other along the circumference of thehousing 20. Similarly, the contact sensor 32 on the tail side includesrectangular detection regions R4 to R6 extending in the axial directionof the housing 20 and curved in the circumferential direction. Thedetection regions R4 to R6 in three locations are arranged in the middleof apexes adjacent to each other along the circumference of the housing20.

Here, the coordinates in the circumferential direction (vertical axis)are defined such that the apexes of the cross-sectional shape are atpositions with angles of 0 degrees, 120 degrees, and 240 degrees in thecircumferential direction. Note that, as can be understood from FIG. 3B,the contact sensors 28 and 32 are provided in relatively flat locations(in other words, sections with large curvature) compared to the apexesof the triangle (0 degrees, 120 degrees, and 240 degrees) on the outerperipheral surface of the housing 20.

The detection regions R1 and R4 are arranged at corresponding positionsin the circumferential direction (positions of center lines are at 60degrees). A length of the detection region R1 in the axial direction isL1, and a length of the detection region R4 in the axial direction isL2. L2 may be the same length as the length of L1 or may be a differentlength. Also, the detection regions R1 and R4 are arranged to be spacedapart from each other by a distance Dis. The distance Dis is a distancedesigned by considering a size of the hand of the user Us and is, forexample, 50 mm or more or 100 mm or more.

The detection regions R2 and R5 are arranged at corresponding positionsin the circumferential direction (positions of center lines are at 180degrees). The detection regions R3 and R6 are arranged at correspondingpositions in the circumferential direction (positions of center linesare at 300 degrees). Note that the detection regions R2 and R5 (ordetection regions R3 and R6) are arranged so as to satisfy the relativepositional relation similar to the detection regions R1 and R4.

FIG. 4 is an electrical block diagram of the stylus 16 illustrated inFIG. 1. In addition to the tip electrode 22 e, the tail electrode 24 e,the tip side sensor group 26, and the tail side sensor group 30 (FIGS.3A and 3B), the stylus 16 includes a power circuit 34, a DC/DC converter36, a tip side transmission circuit 38 (first transmission circuit), atail side transmission circuit 40 (second transmission circuit), and acontrol circuit 42.

The power circuit 34 generates a drive voltage of the stylus 16 andoutputs the obtained direct current (DC) voltage toward the DC/DCconverter 36. Specifically, the power circuit 34 includes a battery 44made of, for example, a lithium-ion battery, and a power management IC(integrated circuit) (hereinafter, PMIC 46) that manages power of thebattery 44.

The DC/DC converter 36 converts the DC voltage input from the powercircuit 34 into DC voltage suitable for each of the circuits and outputsthe DC voltage to each of the tip side transmission circuit 38, the tailside transmission circuit 40, and the control circuit 42.

The tip side transmission circuit 38 is a circuit that generates a pensignal (first downlink signal) based on the DC voltage from the DC/DCconverter 36. The tail side transmission circuit 40 is a circuit thatgenerates an eraser signal (second downlink signal) based on the DCvoltage from the DC/DC converter 36. Each of the tip side transmissioncircuit 38 and the tail side transmission circuit 40 includes anoscillation circuit that generates a carrier wave signal oscillating ata predetermined frequency and a modulation circuit that uses dataincluded in a control signal from the control circuit 42 to modulate thecarrier wave signal. Note that the signal waveform of the carrier wavemay be any alternate current waveform, such as a sine wave, a squarewave, and a triangle wave.

The control circuit 42 is a microcomputer that manages control includinga transmission operation of the downlink signal. The control circuit 42receives detection signals from the tip side sensor group 26 and thetail side sensor group 30 and outputs control signals to the tip sidetransmission circuit 38 and the tail side transmission circuit 40. As aresult, the control circuit 42 can control transmission by the tip sidetransmission circuit 38 and the tail side transmission circuit 40according to a plurality of transmission modes (for example, first,second, and third transmission modes).

The “first transmission mode” here denotes a mode of transmitting thepen signal from the tip electrode 22 e and stopping the transmission ofthe eraser signal from the tail electrode 24 e. Also, the “secondtransmission mode” denotes a mode of stopping the transmission of thepen signal from the tip electrode 22 e and transmitting the erasersignal from the tail electrode 24 e. Also, the “third transmission mode”denotes a mode of transmitting the pen signal from the tip electrode 22e and transmitting the eraser signal from the tail electrode 24 e.

Note that the “pen signal” is a type of downlink signal indicating anintention of using the pen function of the stylus 16 (intension ofmarking). The “eraser signal” is a type of downlink signal indicating anintension of using the eraser function of the stylus 16 (intension ofdeleting a mark). The signal waveforms of the eraser signal and the pensignal are made different from each other in order that the electronicdevice 14 on the receiving side can identify the type of downlinksignal.

In a first method, different data may be used to modulate the carrierwaves with the same frequency, whereby signal waveforms for the erasersignal and the pen signal may be made different. By way of example,information regarding a pen ID or a state of the stylus 16 (for example,pen pressure or posture) can be used in common, and different values canbe used for a specific flag (Invert). Specifically, “Invert” may be setto a value “0” in the case of the pen signal, and “Invert” may be set toa value “1” in the case of the eraser signal. In a second method, thesame data may be used to modulate the carrier waves with differentfrequencies, whereby signal waveforms for the eraser signal and the pensignal may be made different. In a third method, the length of anunmodulated signal may be changed, whereby signal waveforms for theeraser signal and the pen signal may be made different.

<Operation of Stylus 16>

The stylus 16 in the first embodiment is configured in this way. Next,the operation of the stylus 16 (particularly, transmission control bythe control circuit 42) will be described with reference to a flow chartof FIG. 5.

At S1, the control circuit 42 determines whether there is contact to thetip portion 22 or the tail portion 24 based on the detection signalsfrom the end portion sensors 27 and 31. If the tip portion 22 contactsthe touch surface 18, the control circuit 42 determines that only thetip portion 22 is in a contact state (S1: tip) and proceeds to S3described later. Meanwhile, if the tail portion 24 contacts the touchsurface 18, the control circuit 42 determines that only the tail portion24 is in the contact state (S1: tail) and proceeds to S5 describedlater.

In contrast, if the contact state is not detected from either the tipportion 22 or the tail portion 24, the control circuit 42 determinesthat the stylus 16 is in a “hover state” (S1: hover) and proceeds to S2.

At S2, the control circuit 42 determines a grasp state of the stylus 16.Here, the control circuit 42 determines whether the detection signalsfrom the contact sensors 28 and 32 satisfy a predetermined condition(hereinafter, referred to as determination condition) for estimatingthat the stylus 16 is likely in the grasp state. As can be understoodfrom FIG. 1, the typical user Us tends to use a plurality of fingers tograsp the housing 20 (FIGS. 3A and 3B) from the entire circumferentialdirection at a position as close to a leading end side as possible inorder to stabilize writing operation when using the stylus 16.Hereinafter, a specific example of the determination method based on thetendency will be described in detail with reference to FIGS. 6A to 6C.

FIGS. 6A to 6C depict an example of the determination method of thegrasp state and schematically illustrate development diagrams of thehousing 20 as in FIG. 3B. Note that, to facilitate the understanding,hatched rectangles among the detection regions R1 to R6 in a total ofsix locations represent regions in which contact by a human body isdetected, and blank rectangles represent regions in which contact by ahuman body is not detected.

As illustrated in FIG. 6A, it is assumed that contact by a human body issimultaneously detected in the detection regions R1 to R3 in all threelocations on the tip side. Meanwhile, it is assumed that contact by ahuman body is not detected in the detection regions R4 to R6 in allthree locations on the tail side. In this case, the control circuit 42determines that the user Us is in a state of grasping the tip side ofthe stylus 16 with the intention of using the pen function.

As illustrated in FIG. 6B, it is assumed that contact by a human body isnot simultaneously detected in the detection regions R1 to R3 in allthree locations on the tip side. Meanwhile, it is assumed that contactby a human body is simultaneously detected in the detection regions R4to R6 in all three locations on the tail side. In this case, the controlcircuit 42 determines that the user Us is in a state of grasping thetail side of the stylus 16 with the intention of using the eraserfunction.

In this way, whether there is contact by a human body from the entirecircumferential direction of the housing 20 is included as one of thedetermination conditions, and whether the stylus 16 is grasped can beaccurately determined. In addition, the distance Dis between the contactsensors 28 and 32 is set to Dis 100 mm. This can reduce simultaneousdetection by the contact sensors 28 and 32, and the direction of thegrasp of the stylus 16 can be easily determined. Nevertheless, if thecontact sensors 28 and 32 simultaneously detect contact by a human body,determination may be made according to the following rule.

As illustrated in FIG. 6C, it is assumed that contact by a human body issimultaneously detected in the detection regions R1 to R3 in all threelocations on the tip side. Meanwhile, it is determined that contact by ahuman body is detected in the detection region R5 in one location on thetail side. This contact state may be detected when, for example, theuser Us uses a plurality of fingers to grasp the tip side, and at thesame time, the user Us grasps the stylus 16 such that the tail sidecontacts the base of the thumb.

Here, when the number of detected locations on the tip side and thenumber of detected locations on the tail side are the same, the controlcircuit 42 may determine that the user Us grasps the side with a largernumber of detected locations. In the example of FIG. 6C, the controlcircuit 42 determines that the user Us is in the state of grasping thetip side of the stylus 16 with the intention of using the pen function.

At S2 of FIG. 5, if the determination condition of the tip side issatisfied (S2: tip), the control circuit 42 proceeds to S3. In addition,if the determination condition of the tail side is satisfied (S2: tail),the control circuit 42 proceeds to S5. On the other hand, if thedetermination conditions are not satisfied (S2: unknown), the controlcircuit 42 proceeds to S7.

At S3, when the determination is “tip” in one of S1 and S2, the controlcircuit 42 switches the mode and performs the first transmission mode oftransmitting only the pen signal to the outside. Specifically, thecontrol circuit 42 supplies a control signal for generating the pensignal toward the tip side transmission circuit 38 and supplies acontrol signal for stopping the generation of the eraser signal towardthe tail side transmission circuit 40. As a result, the pen signal isgenerated by the tip side transmission circuit 38 and transmitted to theoutside through the tip electrode 22 e (S4).

At S5, when the determination is “tail” in one of S1 and S2, the controlcircuit 42 switches the mode and executes the second transmission modeof transmitting only the eraser signal to the outside. Specifically, thecontrol circuit 42 supplies a control signal for stopping the generationof the pen signal toward the tip side transmission circuit 38 andsupplies a control signal for generating the eraser signal toward thetail side transmission circuit 40. As a result, the eraser signal isgenerated by the tail side transmission circuit 40 and transmitted tothe outside through the tail electrode 24 e (S6).

At S7, when the determination is “hover” at S1 and “unknown” at S2, thecontrol circuit 42 switches the mode and executes the third transmissionmode of transmitting both the pen signal and the eraser signal to theoutside. Specifically, the control circuit 42 supplies a control signalfor generating the pen signal toward the tip side transmission circuit38 and supplies a control signal for generating the eraser signal towardthe tail side transmission circuit 40. As a result, the pen signal istransmitted to the outside through the tip electrode 22 e, and at thesame time, the eraser signal is transmitted to the outside through thetail electrode 24 e (S8). Note that the third transmission mode may befor controlling simultaneous transmission of both the pen signal and theeraser signal or may be for controlling alternate time-divisiontransmission of the pen signal and the eraser signal.

The operation of the flow chart illustrated in FIG. 5 ends in this way.The control circuit 42 repeats the flow chart at each predeterminedexecution cycle, and the stylus 16 can successively transmit thedownlink signals to the electronic device 14.

<Advantageous Effects of First Embodiment>

As described above, the stylus 16 includes the cylindrical housing 20,the tip portion 22 provided on the tip side of the housing 20 andincluding the tip electrode 22 e, a tail portion 24 provided on the tailside of the housing 20 and including the tail electrode 24 e, the powercircuit 34 provided in the housing 20, the tip side transmission circuit38 (first transmission circuit) that receives power from the powercircuit 34 to generate the pen signal (first downlink signal)transmitted toward the outside of the housing 20 through the tipelectrode 22 e, the tail side transmission circuit 40 (secondtransmission circuit) receiving power from the power circuit 34 togenerate the eraser signal (second downlink signal) which is a signaltransmitted toward the outside of the housing 20 through the tailelectrode 24 e and is different from the pen signal, and the controlcircuit 42 controlling the transmission by the tip side transmissioncircuit 38 and the tail side transmission circuit 40 according to theplurality of transmission modes.

The plurality of transmission modes include the first transmission modeof performing the transmission control for transmitting the pen signalfrom the tip electrode 22 e and stopping the transmission of the erasersignal from the tail electrode 24 e, and the second transmission mode ofperforming the transmission control for stopping the transmission of thepen signal from the tip electrode 22 e and generating the eraser signalfrom the tail electrode 24 e. In the hover state in which both the tipportion 22 and the tail portion 24 do not contact the touch surface 18of the electronic device 14 including the touch sensors, the controlcircuit 42 switches and executes the first transmission mode and thesecond transmission mode based on the determination regarding the graspstate of the housing 20.

In this way, the first transmission mode and the second transmissionmode are switched and executed based on the determination regarding thegrasp state of the housing 20, and only the downlink signal suitable forthe grasp state of the housing 20 can be alternatively transmitted inadvance in the hover state. As a result, in the configuration in whichthe downlink signals can be transmitted from both the tip side and thetail side, the consumption of electrical energy can be reduced while theoperation response is secured.

In addition, the stylus 16 may further include a contact sensor 28(first contact sensor) that detects whether the user Us contacts thehousing 20 near the tip portion 22, and the control circuit 42 maycontrol the transmission according to the first transmission mode whenthe contact sensor 28 detects the contact. The contact near the tipportion 22 is likely to be detected when the user Us uses the tip sideof the stylus 16, and this knowledge based on human engineering is usedto further improve determination accuracy of the grasp state.

In addition, the contact sensor 28 may be provided in at least threelocations along the circumference of the housing 20, and the controlcircuit 42 may control the transmission according to the firsttransmission mode when the contact sensor 28 detects contact in three ormore locations. The contact by a plurality of fingers from the entirecircumferential direction is likely to be simultaneously detected whenthe user Us uses the tip side of the stylus 16, and this knowledge basedon human engineering is used to further improve the determinationaccuracy of the grasp state.

In addition, the stylus 16 may further include the contact sensor 32(second contact sensor) that detects whether the user Us contacts thehousing 20 near the tail portion 24, and the control circuit 42 maycontrol: (a) the transmission according to the first transmission modewhen the contact sensor 28 detects the contact and the contact sensor 32does not detect the contact; and (b) the transmission according to thesecond transmission mode when the contact sensor 28 does not detect thecontact and the contact sensor 32 detects the contact. This can securethe operation response and reduce the energy consumption when either oneof the tip side and the tail side of the stylus 16 is used.

In addition, the plurality of transmission modes may further include thethird transmission mode of performing transmission control fortransmitting the pen signal from the tip electrode 22 e and transmittingthe second downlink signal from the tail electrode 24 e, and the controlcircuit 42 may execute the third transmission mode when the grasp stateof the housing 20 is not determined. The pen signal and the erasersignal can be transmitted to secure the operation response of the stylus16 even when one of the tip portion 22 and the tail portion 24 contactsthe touch surface 18 with the grasp state not determined.

In addition, the contact sensor 28 and the contact sensor 32 may bearranged to be spaced apart from each other by 100 mm or more in theaxial direction of the housing 20. This can reduce the simultaneousdetection by the contact sensors 28 and 32, and the direction of thegrasp of the stylus 16 can be easily determined.

In addition, each of the contact sensors 28 and 32 may be provided inthe same number of locations along the circumference or the axis of thehousing 20, and the control circuit 42 may control: (a) the transmissionaccording to the first transmission mode when the number of detectedlocations of the contact by the contact sensor 28 is greater than thenumber of detected locations of the contact by the contact sensor 32;and (b) the transmission according to the second transmission mode whenthe number of detected locations of the contact by the contact sensor 28is smaller than the number of detected locations of the contact by thecontact sensor 32. As a result, the direction of the grasp of the stylus16 can be accurately determined even when the contact sensors 28 and 32simultaneously detect the contact by a human body.

In addition, the contact sensors 28 and 32 may be provided in relativelyflat locations on the outer peripheral surface of the housing 20compared to other locations. The flatter the detected location ofcontact is, the more the finger of human body will come into closecontact with the detected location. This further improves the detectionaccuracy of the contact sensors 28 and 32.

<Modifications of First Embodiment>

First Example

The detection regions R1 to R6 of the contact sensors 28 and 32 are notlimited to the example illustrated in FIG. 3B, and the shape, thepositions, or the number of detection regions can be appropriatelychanged.

FIGS. 7A and 7B are external views of a stylus 60 according to a firstmodification of the first embodiment. More specifically, FIG. 7A is aside view of the stylus 60, and FIG. 7B is a partial development diagramof the housing 20. As illustrated in FIG. 7A, in addition to the housing20, the tip portion 22, and the tail portion 24, the stylus 60 includescontact sensors 62 and 64 shaped differently from the first embodiment(contact sensors 28 and 32).

As illustrated in FIG. 7B, the contact sensor 62 on the tip sideincludes annular detection regions R1, R2, and R3 from the tip sidetoward the center. The detection regions R1 to R3 in three locations arearranged at regular intervals in the axial direction of the housing 20.Similarly, the contact sensor 64 on the tail side includes annulardetection regions R4, R5, and R6 from the tail side toward the center.The detection regions R4 to R6 in three locations are arranged atregular intervals in the axial direction of the housing 20. Note thatthe detection regions R3 and R4 in two locations are arranged to bespaced apart from each other by a distance Dis. The distance Dis is, forexample, 50 mm or more or 100 mm or more.

Even when the shapes of the contact sensors 62 and 64 are changed inthis way, the grasp state of the housing 20 can be determined as in thefirst embodiment. Particularly, there is an advantage that the annularshape of the detection regions R1 to R6 allows to obtain uniformdetection sensitivity regardless of the rotation posture (angle) of thestylus 60.

Second Example

The shape of the housing 20 is not limited to the example illustrated inFIG. 3A, and the shape can be appropriately changed. For example, across section of the housing 20 may be a circle or a polygon, or part ofthe housing 20 may be processed to allow the user Us to easily grasp thehousing 20.

FIGS. 8A and 8B are external views of a stylus 70 according to a secondmodification of the first embodiment. More specifically, FIG. 8A is afront view of the stylus 70 as viewed from the tip side, and FIG. 8B isa rear view of the stylus 70 as viewed from the tail side. In additionto the tip portion 22 and the tail portion 24, the stylus 70 includes ahousing 72 shaped differently from the first embodiment.

As illustrated in FIG. 8A, a cross-sectional shape of the housing 72 isa Reuleaux triangle as in the first embodiment (housing 20). A recessedportion 78 including a flat receiving surface 76 is formed at a positionon an outer peripheral surface 74 of the housing 72, near the tipportion 22. A contact sensor 80 (first contact sensor) that detectscontact by a human body is provided on at least the receiving surface76.

As illustrated in FIG. 8B, a recessed portion 84 including a flatreceiving surface 82 is formed at a position on the outer peripheralsurface 74 of the housing 72, near the tail portion 24. Also, a contactsensor 86 (second contact sensor) that detects contact by a human bodyis provided on at least the receiving surface 82.

Even when the shape of the housing 72 is changed in this way, the graspstate of the housing 72 can be determined as in the first embodiment.Particularly, the thumb of the user Us is induced to contact thereceiving surface 76 of the recessed portion 78 (or the receivingsurface 82 of the recessed portion 84) when the user Us grasps thestylus 70, and this further improves the detection accuracy of thecontact sensors 80 and 86.

Third Example

Although the contact sensors 28 and 32 are used to determine the graspstate in the first embodiment, other sensors (particularly, sensorsprovided for other purposes) may be used in place of the contact sensors28 and 32. For example, the control circuit 42 may control: (a) thetransmission according to the first transmission mode when the endportion sensor 27 detects the most recent contact to the touch surface18; and (b) the transmission according to the second transmission modewhen the end portion sensor 31 detects the most recent contact to thetouch surface 18. It is likely that one of the tip portion 22 and thetail portion 24 that most recently contacts the touch surface 18 will becontinuously used, and this is taken into account to further improve thedetermination accuracy of the grasp state.

Fourth Example

Although the first embodiment does not assume a case in which contact toboth the tip portion 22 and the tail portion 24 is detected, a processof this case may be also executed. For example, the stylus 16 may be putin a bag or the like when contact to both the tip portion 22 and thetail portion 24 is detected. Therefore, the control circuit 42 maycontrol the transmission to stop the transmission of the pen signal fromthe tip electrode 22 e and to stop the transmission of the eraser signalfrom the tail electrode 24 e. This can prevent consumption of electricalenergy in an unexpected state.

Second Embodiment

Next, a stylus 102 according to a second embodiment will be describedwith reference to FIGS. 9 to 11. Note that the same reference charactersare provided to the components and the functions similar to the firstembodiment, and the components and the functions may not be described.

<Overall Configuration of Position Detection System 100>

As illustrated in FIG. 1, a position detection system 100 basicallyincludes the electronic device 14 and the stylus 102. Note that theconfiguration of the electronic device 14 can be the same as ordifferent from the configuration illustrated in FIG. 2.

<Configuration of Stylus 102>

FIG. 9 is an external view of the stylus 102 according to the secondembodiment, and FIG. 9 illustrates a state in which a tip portion 104 isgrasped so as to face the touch surface 18. The stylus 102 includes thecylindrical housing 20, the tip portion 104 provided on the tip side ofthe housing 20, and a tail portion 106 provided on the tail side of thehousing 20.

In addition to the tip electrode 22 e and the tip cover 22 c, the tipportion 104 in a roughly conical shape includes a ring electrode 108made of a conductive material. The ring electrode 108 is an electrodereceiving an uplink signal and is provided inside or outside of the tipcover 22 c. Unlike the configuration of the first embodiment, only theend portion sensor 27 is provided on the tip side of the housing 20.

In addition to the tail electrode 24 e and the tail cover 24 c, the tailportion 106 in a roughly conical shape includes a ring electrode 110made of a conductive material. The ring electrode 110 is an electrodereceiving an uplink signal and is provided inside or outside of the tailcover 24 c. Unlike the configuration of the first embodiment, only theend portion sensor 31 is provided on the tail side of the housing 20.

Incidentally, the sensor control circuit 202 on the electronic device 14side receives the downlink signal from the stylus 102 through the sensorelectrode 200 connected to the control circuit 202. The sensor controlcircuit 202 then generates an uplink signal including data correspondingto the type of the received downlink signal and transmits the uplinksignal through the sensor electrode 200.

In the example of FIG. 9, the tip electrode 22 e is at a position closeto the touch surface 18 (sensor electrode 200) compared to the tailelectrode 24 e. Under this positional relation, the electronic device 14can receive the pen signal from the tip electrode 22 e through thesensor electrode 200, and the stylus 102 can receive the uplink signalfrom the sensor electrode 200 through the ring electrode 108.Conversely, the electronic device 14 cannot receive the eraser signalfrom the tail electrode 24 e through the sensor electrode 200, and thestylus 102 cannot receive the uplink signal from the sensor electrode200 through the ring electrode 110.

FIG. 10 is an electrical block diagram of the stylus 102 illustrated inFIG. 9. The stylus 102 includes the tip electrode 22 e, the tailelectrode 24 e, the end portion sensors 27 and 31, the power circuit 34,the DC/DC converter 36, the tip side transmission circuit 38, the tailside transmission circuit 40, the ring electrodes 108 and 110, and acontrol circuit 112.

The control circuit 112 is a microcomputer that manages the controlincluding the transmission operation of the downlink signal. The controlcircuit 112 receives detection signals from the end portion sensors 27and 31 and uplink signals from the ring electrodes 108 and 110 andoutputs control signals to the tip side transmission circuit 38 and thetail side transmission circuit 40. As a result, the control circuit 112can control the transmission by the tip side transmission circuit 38 andthe tail side transmission circuit 40 according to at least the first,second, and third transmission modes.

<Operation of Stylus 102>

The stylus 102 in the second embodiment is configured in this way. Next,the operation of the stylus 102 (particularly, transmission control bythe control circuit 112) will be described in detail with reference to aflow chart of FIG. 11.

At S11, the control circuit 112 determines whether there is contact tothe tip portion 104 or the tail portion 106 based on the detectionsignals from the end portion sensors 27 and 31. If the tip portion 104contacts the touch surface 18, the control circuit 112 determines thatonly the tip portion 104 is in the contact state (S11: tip) and proceedsto S14 described later. On the other hand, if the tail portion 106contacts the touch surface 18, the control circuit 112 determines thatonly the tail portion 106 is in the contact state (S11: tail) andproceeds to S16 described later.

On the other hand, if the contact state is not detected from either thetip portion 104 or the tail portion 106, the control circuit 112determines that the stylus 102 is in the “hover state” (S11: hover) andproceeds to S12.

At S12, the control circuit 112 determines whether the uplink signalsare received through the ring electrodes 108 and 110. If the uplinksignals are not received (S12: NO), the control circuit 112 proceeds toS20 described later. On the other hand, if the uplink signals arereceived (S12: YES), the control circuit 112 proceeds to S13.

At S13, the control circuit 112 determines the grasp state of the stylus102. Here, the control circuit 112 uses the data included in thereceived uplink signals to determine the grasp state. As can beunderstood from FIG. 9, the stylus 102 is grasped at a position close tothe touch surface 18 of the electronic device 14 during the use. Thecloser the transmission position of the downlink signal to the touchsurface 18 is, the higher the possibility of the reception of the signalby the electronic device 14 tends to be. Hereinafter, a specific exampleof a determination method based on the tendency will be described.

First, the sensor control circuit 202 on the electronic device 14 sidechanges part (hereinafter, referred to as identifier) of the data to betransmitted according to the reception status of the downlink signal.The identifier indicates the type of downlink signal most recentlyreceived by the electronic device 14. The identifier is binary (1 bit),indicating “0” for the pen signal and “1” for the eraser signal.

For example, the sensor control circuit 202 sets the identifier to “0”when the pen signal is continuously received for longer than apredetermined time or more than a predetermined number of times. Thesensor control circuit 202 sets the identifier to “1” when the erasersignal is continuously received for longer than a predetermined time ormore than a predetermined number of times. The sensor control circuit202 sets the identifier to “NULL” in other cases. The sensor controlcircuit 202 then generates an uplink signal including the identifier andtransmits the uplink signal through the sensor electrode 200.

The control circuit 112 analyzes the data indicated by the receiveduplink signal and determines the grasp state according to the value ofthe identifier included in the data. More specifically, when theidentifier is “0,” the control circuit 112 determines that the user Usis grasping the tip side of the stylus 102 with the intention of usingthe pen function. Also, when the identifier is “1”, the control circuit112 determines that the user Us is grasping the tail side of the stylus102 with the intention of using the eraser function. Also, when theidentifier is “NULL,” the control circuit 112 determines that the graspstate is unknown.

Conversely, the identifier may indicate the type of downlink signal notmost recently received by the electronic device 14. In this case, thecontrol circuit 112 determines that the user Us is not grasping the tipside of the stylus 102 when the identifier is “0” and determines thatthe user Us is not grasping the tail side of the stylus 102 when theidentifier is “1.”

If the determination condition of the tip side is satisfied (S13: tip),the control circuit 112 proceeds to S14. Also, if the determinationcondition of the tail side is satisfied (S13: tail), the control circuit112 proceeds to S16. On the other hand, if the determination conditionsare not satisfied (S13: unknown), the control circuit 112 proceeds toS18.

At S14, when the determination is “tip” in one of S1 l and S13, thecontrol circuit 112 switches the mode and executes the firsttransmission mode of transmitting only the pen signal to the outside. Asa result, the pen signal is generated by the tip side transmissioncircuit 38 and transmitted to the outside through the tip electrode 22 e(S15).

At S16, when the determination is “tail” in one of S1 l and S13, thecontrol circuit 112 switches the mode and executes the secondtransmission mode of transmitting only the eraser signal to the outside.As a result, the eraser signal is generated by the tail sidetransmission circuit 40 and transmitted to the outside through the tailelectrode 24 e (S17).

At S18, when the determination is “hover” at S1 l and “NO” at S13, thecontrol circuit 112 switches the mode and executes the thirdtransmission mode of transmitting both the pen signal and the erasersignal to the outside. As a result, the pen signal is transmitted to theoutside through the tip electrode 22 e, and at the same time, the erasersignal is transmitted to the outside through the tail electrode 24 e(S19).

At S20, when the determination is “NO” at S12, the control circuit 112is not receiving a command from the electronic device 14 side (that is,transmission trigger of downlink signal), and the control circuit 112transmits neither the pen signal nor the eraser signal.

The operation of the flow chart illustrated in FIG. 11 ends in this way.The control circuit 112 repeats the flow chart at each predeterminedexecution cycle, and the stylus 102 can successively transmit thedownlink signals to the electronic device 14.

<Advantageous Effects of Second Embodiment>

In this way, in addition to the housing 20, the tip portion 104, thetail portion 106, the power circuit 34, the tip side transmissioncircuit 38, and the tail side transmission circuit 40, the stylus 102includes the control circuit 112 that switches and executes the firsttransmission mode and the second transmission mode based on thedetermination regarding the grasp state of the housing 20 in the hoverstate. The control circuit 112 uses the data included in the uplinksignal received from the electronic device 14 to determine the graspstate of the housing 20. As a result, in the configuration in which thedownlink signals can be transmitted from both the tip side and the tailside, the consumption of electrical energy can be reduced while theoperation response is secured, as in the first embodiment.

Also, the data may include the identifier indicating the type ofdownlink signal received by the electronic device 14, and the controlcircuit 112 may control: (a) the transmission according to the firsttransmission mode when the identifier indicates the pen signal; and (b)the transmission according to the second transmission mode when theidentifier indicates the eraser signal.

Conversely, the data may include the identifier indicating the type ofdownlink signal not received by the electronic device 14, and thecontrol circuit 112 may control: (a) the transmission according to thefirst transmission mode when the identifier indicates the eraser signal;and (b) the transmission according to the second transmission mode whenthe identifier indicates the pen signal.

Also, the plurality of transmission modes may further include the thirdtransmission mode of performing transmission control for transmittingthe pen signal from the tip electrode 22 e and transmitting the erasersignal from the tail electrode 24 e, and the control circuit 112 mayexecute the third transmission mode when the grasp state of the housing20 is not determined. The pen signal and the eraser signal can betransmitted to secure the operation response of the stylus 102 even whenone of the tip electrode 22 e and the tail electrode 24 e contacts thetouch surface 18 with the grasp state not determined.

The sensor control circuit 202 that realizes the operation describedabove receives the downlink signal from the stylus 102 through theconnected sensor electrode 200, generates the uplink signal includingthe data corresponding to one of the pen signal and the eraser signalreceived, and transmits the uplink signal through the sensor electrode200.

Here, the data may be used for controlling the transmission by thestylus 102 to continue the transmission of one of the pen signal and theeraser signal. Conversely, the data may be used for controlling thetransmission by the stylus 102 to stop the transmission of one of thepen signal and the eraser signal.

<Modification of Second Embodiment>

Although the ring electrodes 108 and 110 are used to receive the uplinksignal in the second embodiment, the tip electrode 22 e or the tailelectrode 24 e may be used to receive the uplink signal instead. Forexample, when the uplink signal is transmitted and received through thetip electrode 22 e, a switchable switch mechanism can be provided to:[1] connect the tip electrode 22 e and the transmission circuit duringthe transmission of the pen signal; and [2] connect the tip electrode 22e and the reception circuit during the reception of the uplink signal.

It is to be noted that the embodiment of the present disclosure is notlimited to the foregoing embodiment, and that various changes can bemade without departing from the spirit of the present disclosure.

What is claimed is:
 1. A stylus comprising: a housing; and a capacitivetouch sensor having multiple sensing elements distributedcircumferentially and longitudinally along the housing.
 2. The stylus ofclaim 1, further comprising an antenna assembly.
 3. The stylus of claim1, wherein the housing has a longitudinal portion forming asubstantially flat exterior surface extending along a length of thestylus.
 4. A stylus comprising: a housing having a longitudinal portionforming a substantially flat exterior surface extending along a lengthof the stylus; and a capacitive touch sensor comprising multiple sensingelements distributed circumferentially and longitudinally along thehousing.
 5. The stylus of claim 4, further comprising an antennaassembly.
 6. A stylus comprising: a housing; and a capacitive touchsensor including a plurality of detection regions arranged along acircumference of the housing, wherein at least some of the detectionregions are spaced apart from each other in an axial direction of thehousing.
 7. The stylus of claim 6, wherein each of the detection regionsextends in the axial direction of the housing and a circumferentialdirection of the housing.
 8. The stylus of claim 6, further comprisingat least one electrode which, in operation, receives an uplink signalfrom an external device.
 9. The stylus of claim 8, wherein the at leastone electrode includes a first electrode at a first end of the housingin the axial direction of the housing, and a second electrode at asecond end of the housing in the axial direction of the housing.
 10. Thestylus of claim 6, wherein a portion of the housing has a flat exteriorsurface extending in the axial direction of the housing.
 11. The stylusof claim 6, further comprising: a signal transmission circuit; and acontrol circuit which, in operation, controls the signal transmissioncircuit based on one or more detection signals received from thecapacitive touch sensor.